Ionic strength dependent kinetics of nanocolloidal gold deposition

The deposition kinetics of the irreversible adsorption of citrate-stabilized, nanocolloidal gold particles on Si/SiO2 surfaces, derivatized with (aminopropyl)triethoxysilane, is investigated in situ using single wavelength reflectometry. A well-defined flow of colloids toward the surface is realized using a radial impinging jet cell geometry. The saturation coverage after prolonged deposition can be analyzed in terms of random sequential adsorption and depends on the ionic strength of the solution, in good agreement with DLVO theory. Atomic force microscopy measurements indicate that for higher coverages, the formation of particle clusters gives rise to a deviation from DLVO behavior. After a short transition time, the dynamics of the deposition process is at first mass transport limited. Surface blocking effects determine the adsorption kinetics in the final stage. The entire deposition process can be adequately described in terms of a generalized adsorption theory, which combines the effects of mass transport and the actual adsorption onto the surface.